In recent years, with enhancement of performance of two-wheeled automotive vehicles, two-wheeled automotive vehicle tires are required to have high-speed-durability performance. For example, as shown in FIG. 5, a two-wheeled automotive vehicle tire a has been known in which a tread rubber bg includes: a cap layer c forming an outer surface bs of a tread portion b; and a base layer d disposed inward of the cap layer in the tire radial direction, and the base layer d is formed of a rubber having a loss tangent tan δ reduced, in order to enhance the high-speed-durability performance.
In the two-wheeled automotive vehicle tire a thus formed, since the base layer d is formed of a rubber in which heat emission is reduced, the tread rubber bg can be effectively restrained from being subjected to thermal destruction (becoming porous) to be in a sponge-like state due to heat emission during high speed running, thereby enabling improvement of high-speed-durability performance. Further, the base layer d is formed of a rubber having a small hysteresis loss, and therefore rolling resistance performance can be also improved. The related art is as follows.